To achieve those results requires a lot of effort, and hardcore optimisation. Native coding gets you the same results, minus all that effort (as long as you're okay with targeting one platform), so yeah I was sort of saying it doesn't count IMO :)
That said, I'm building all my applications using web tools, Facebooks React allows for some amazing native performance, cross platform! If the views are decoupled enough, you can get two UIs with the exact same logic client and server side, with near native performance to boot.
Now it's not there yet, but it's super close, and once tooling is built up to tackle this use case with the new tech and architecture (client side), then I think it'll be a very big deal!
How often are you jumping between iOS and android that this is an actual, real concern?